Apparatus for roll forming toothed workpieces

ABSTRACT

Apparatus for forming toothed workpieces by rolling them in high-pressure contact with a single forming die. The workpieces are held in precise relation with the die during at least the final stage of the rolling operation by a support assembly having one or more pilot surfaces, each pilot surface being in rolling contact with a pair of rigidly mounted backup members. The pilot surface or surfaces and the backup members locate the axis of the workpiece with respect to the axis of the forming roll. Separate support members positively locate the workpiece along its axis during the rolling operation.

United States Patent APPARATUS FOR ROLL FORMING TOOTHED WORKPIECES 3Claims, 4 Drawing Figs.

U.S. Cl 72/102, 29/1 592 Int. Cl B2lh 5/02 Field of Search 72/ l 02,

I07, 108, 109, HO, lll;29/l59.2

[56] References Cited UNITED STATES PATENTS 3,552,167 l/l97l Bergietal29/l59.2 3,434,322 3/1969 Cowles et al 72/107 Primary ExaminerL0well A.Larson Attorney-Strauch, Nolan, Neale, Nies & Kurz ABSTRACT: Apparatusfor forming toothed workpieces by rolling them in highpressure contactwith a single forming die. The workpieces are held in precise relationwith the die during at least the final stage of the rolling operation bya support assembly having one or more pilot surfaces, each pilot surfacebeing in rolling contact with a pair of rigidly mounted backup members.The pilot surface or surfaces and the backup members locate the axis ofthe workpiece with respect to the axis of the forming roll. Separatesupport members positively locate the workpiece along its axis duringthe rolling operation.

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SHEET 1 0F 3 INVENTORS JOHN LEONARD MARTIN S. WENGERJR INVENTORS @OHNLEONARD MARTIN s. WENGER, JR

BY I a ATTORN S SHEET 2 UP 3 PATENTED JAN 41972 a 1 L mm a PATENTEUJAN41972 SHEET 3 [IF 3 INVENTORS JOHN LEONARD MARTIN S. WENGER, JR

APPARATUS FOR ROLL FORMING TOOTIIED WORKPIECES BACKGROUND OF THEINVENTION This invention relates to apparatus for roll forming toothedworkpieces and has particular application to the formation of parts,such as automotive transmission gears, which must meet unusuallyexacting standards for dimensional accuracy and quality of finish. Thetraditional method of manufacturing such parts by first hobbing acylindrical blank and forming the part to final dimensions by shavinghas now been replaced in many operations by a technique which comprisessubstituting for the final shaving operation a roll finishing operation.Examples of roll finishing apparatus are disclosed in US. Pat. No.3,362,059 and in copending application Ser. No. 809,365 filed Mar. 21,1969 for Apparatus for Roll Forming Workpieces and application Ser. No.817,669 filed Apr. 21, 1969 for Apparatus for Roll Forming workpieces.

In the apparatus disclosed in the patent, the workpiece is rotatablymounted between a pair of rotating dies, one of which rotates about afixed axis and the other of which rotates about a laterally displaceableaxis. In operation, the moveable die is shifted toward the fixed axisdie and the workpiece is engaged under high pressure at peripherallyopposed points by the two dies. Despite its many advantages and itsexcellent performance this type of apparatus is sufficiently expensiveto be feasible only in environments where high production rates are therule. The high cost of the machine is due in part to the requirement fora pair of forming rolls or dies which are exactly matched and which mustbe installed and operated with the utmost precision to maintain the twodies in matched relationship with the required accuracy.

An important simplification of the prior apparatus is disclosed in theaforesaid copending application Ser. No. 817,669. In the apparatusdisclosed therein the workpiece is typically mounted for rotation on asupport between a pair of arbors, one of which is driven and carries aforming die or roll. The opposed arbor carries one or more pilot membershaving essentially cylindrical surfaces which run in rolling contactwith the cylindrical surfaces of corresponding pilot members carried byand rotatable with the workpiece support structure. Thus, the priorapparatus, by transferring the rolling loads to the pilot surfaces andthence to the heavy machine base permitted the use of a single die toeffect the rolling operation.

It is recognized that the accuracy with which the workpiece is formed isdependent on the rigidity with which the workpiece is supported duringthe rolling operation. Experience has shown that it is whollyimpractical to provide a rotatable workpiece support having sufficientresistance to deflection and having sufficient precision to assurepositioning of the workpiece throughout the forming operation with therequired accuracy.

While the apparatus of application Ser. No. 817,669 eliminates the needfor a second forming die to absorb the rolling loads it continues torely on the workpiece support to locate the workpiece positively in twoplanes i.e. in a plane normal to the planes containing the axes of theforming roll and the workpiece and in a plane normal to these axes.Accordingly the prior apparatus retains the requirement for a relativelymassive, high precision work support assembly.

SUMMARY OF THE INVENTION It is the principal purpose and object of thepresent invention to provide improved apparatus for roll forming toothedworkpieces, such as gears, which efiects an important simplification inprior apparatus and a corresponding reduction in cost while effectingthe production of finished parts having an accuracy equal to or betterthan the best prior available apparatus.

In obtaining this and other objects the present invention provides gearforming apparatus in which the workpieces are formed to finalconfiguration by rotating them in high-pressure engagement with a singleforming die carried by a driven arbor. Typically, the workpiece iscentrally apertured and is carried on a support assembly comprising apair of axially aligned support members, one of which engages theworkpiece aperture. The support members preferably are each providedwith a cylindrical pilot surface concentric with the workpiece axis anddisposed closely adjacent to a side surface of the workpiece. Each ofthe pilot surfaces runs in rolling contact with a pair of cylindricalbackup members rotatably mounted on the machine structure which carriesthe forming die.

In operation the backup members absorb the full rolling load. The axesof the backup members are offset equally from the plane containing theaxes of forming roll and the workpiece. Accordingly the backup membersalso absorb any force developed during the rolling operation which tendsto move the axis of the workpiece out of the plane containing the axisof the roll and the axis of the workpiece.

Thus the workpiece support assembly is required to absorb only therelatively minor forces developed during rolling which tend to move theworkpiece along its axis. The absorption of these forces is accomplishedby a two part support assembly, each part having a surface engageablewith a side surface of the workpiece. Each support part is moveableaxially of the workpiece, one part being axially moveable to apredetermined position to positively locate the workpiece, the otherpart clamping the workpiece in its located position.

As a further feature of the invention, the forming roll, workpiecesupport assembly, and backup members are so arranged as to provideautomatic gauging of the size of the workpiece inserted into theapparatus. This arrangement automatically prevents the insertion of aworkpiece which is sufficiently oversize to damage the apparatus.

Additional objects, features and advantages of the invention will becomeapparent as the description proceeds.

DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a gear finishingapparatus constructed in accordance with the present invention;

FIG. 2 is an enlarged front view of the apparatus shown in FIG. 1;

FIG. 3 is a transverse section taken along line 33 of FIG. 2 showingdetails of the workpiece support apparatus; and

FlG. 4 is a vertical section taken along line 4-4 of FIG. 2 showingfurther details of construction.

DESCRIPTION OF PREFERRED EMBODIMENT The rolling apparatus of the presentinvention comprises a base structure indicated generally at 20 by whicha head assembly 22 is supported upon an upwardly projecting rigid column24. To impart further rigidity to the assembly the head section 22 isconnected to an opposing head section 21 by a pair of tie bars 26 and28. An upper spindle assembly, indicated generally at 30, is rotatablysupported in a trunnion assembly 32 carried by a column 34 projectingdownwardly from the head section 22. The spindle assembly is driven byany convenient means for example a hydraulic motor 36. Convenn'onalmechanisms are included in the trunnion assembly 32 and the column 34 topermit all of the required adjustments, the axis of the upper spindleassembly 30 is fixed. A die 38 preferably of the type disclosed inapplication Ser. No. 809,365 is rigidly secured to the upper spindle forrotation therewith about an axis concentric with the axis of the spindleassembly.

The workpiece W is carried by a support assembly, illustrated in detailin FIG. 3, comprising a pair of identical arbors 40 and 42 and a pair offittings 44 and 46. The arbors 40 and 42 are mounted for axial movementand for rotation in housings 47 and 48, respectively, carried by a framestructure 49 supported for vertical movement on a pair of verticalshafts 50 and 52 carried in suitable fittings rigid with the rearmachine column 24. The frame assembly 49 is biased upwardly by a spring54 mounted centrally of the frame assembly.

The arbor assembly 40 is mounted in precision bearings 56 for rotationand axial sliding movement within the housing 47 and at its inner end isconnected through a series of thrust bearings 58 to a fitting 60 on theend of a piston rod 62 projecting from a hydraulic motor 64 carried bythe housing 47. The arbor 42 is similarly mounted in the housing 48 andsimilarly connected to the piston of a somewhat smaller opposedhydraulic motor 66. Each of the arbors 40 and 42 carry a spring loadedcentering pin such as that shown at 67.

The fitting 44 has a flat end face 68 adapted to engage the flat endface of the arbor 40 and a central recess 70 for engagernent by thecentering pin 67. The fitting has an opposed radial surface 72 adaptedto engage the side surface of the workpiece W. A cylindrical section 74on the fitting 44 projects through central aperture 76 of the workpiecein close clearance relation thereto and into a cylindrical recess 78 inthe fitting 46. A reduced end portion 80 of the cylindrical projection74 is provided with a central recess 82 to receive the centering pinassociated with the arbor 42. Accordingly, the workpiece is initiallypositively located with respect to the fittings 44 and 46 which as aunit, are positively initially located by the arbors 40 and 42. Themotor 66 is either smaller than the motor 64 or is supplied with fluidunder reduced pressure. Accordingly, when the arbors 40 and 42 areadvanced, the arbor 40 reaches the limit position determined by a stop,not shown, which may be located internally of the motor 64. The arbor 42is not permitted to reach a stop so it constantly urges the fitting 46against the side face of the workpiece to urge the opposite side faceagainst the locating surface 72 on the fitting 44. This arrangementassures the proper location of the workpiece along its own axis. Thearbors 40 and 42, however, are totally inadequate to absorb, withacceptable deflection, the loads imposed on the workpiece during therolling operation.

The unique apparatus provided to absorb these loads includes thefittings 44 and 46 and associated pairs of backup members 84, 86 and 88,90. The backup members 84 and 88 are preferably carried by a commonshaft 92 and the backup members 86'and 90 are similarly carried by acommon shaft 94. The shafts 92 and 94 are mounted in upwardly projectingarms 96 and 98 carried by a frame assembly 100 supported on slideways102 and 104 for movement in a directional normal to the plane containingthe axis of the die 38 and the workpiece W. Slideways I02 and 104 areformed on the head assembly 106 of a conventional hydraulic ram, notshown, mounted to the lower machine head 21. As explained below, the ramis effective to raise the workpiece into rolling engagement with the die38 and subsequently lower the workpiece after the rolling operation hasbeen completed.

The frame assembly 100 carrying the backup members 84-90 is movedbetween the full line operating position shown in FIG. 4 and the dottedline loading position by a toggle mechanism 108. When the togglemechanism is operated by movement of the handle 110 in a clockwisedirection as viewed in FIG. 4, a rod 112 attached to the togglemechanism and the frame assembly 100 withdraws the latter to the right.

When the machine is at rest, the arbors 40 and 42 are separated and thearbors and backup members are lowered. The machine may be readied forloading by manipulating the toggle mechanism 108 to withdraw the backuprollers and associated structure to the dotted line position FIG. 4. Theworkpiece and the fitting 46 are successively assembled on the fitting44. This subassembly is then positioned in place on the backup rollers84-90 to dispose the cylindrical surface 1 14 of the fitting 44 inengagement with the corresponding cylindrical surfaces of the backupmembers 88 and 90 and the cylindrical surface 116 on the fitting 46 incontact with the corresponding cylindrical surfaces of the backupmembers 84 and 86.

The toggle mechanism 108 is then manipulated to move the parts to thefull line position of FIG. 4. Suitable adjustable stops areprovided todispose the axes of the backup rollers in the proper relationship to aplane containing the axis of the die 38 and the workpiece W. It is afeature of the invention that the distance between the shafts 92 and 94and the axis of the die 38 is such that when the hydraulic ram islowered a properly sized workpiece can be easily moved into position butan oversized workpiece will be blocked thus preventing the inadvertantloading of an oversized workpiece which might cause breakage of the die.

With the workpiece in proper position the arbors 40 and 42 are advancedtoward each other and the ends of the locating pins 67 enter therecesses provided in the fittings 44 and 46. As explained above theadvancement of the arbor 40 continues until it abuts against a positivestop and the arbor 42 tightly clamps the workpiece in its proper axialposition.

After the workpiece has been thus located the rolling operation isinitiated manually and thereafter performed automatically. When theoperator depresses a suitable start button a two piece sheet metalshield assembly 118 is automatically raised to cover the front of themachine. The motor 36 is then operated to drive the die 38 which is inrolling engagement with the workpiece W. In accordance with theconventional practice coolant is supplied throughout the rollingoperation. The main hydraulic ram is then energized to raise the head100 together with the backup members 84-90 which in turn act on thefittings 44 and 46 to raise the workpiece, the arbors 40 and 42 and theassociated frame structure 49 to bring the workpiece into pressureengagement with the die. The upward movement of the parts isautomatically arrested, the die and the workpiece are rotated through asuitable dwell period and the parts are then lowered. The operation ofthe drive motor 36 is discontinued and the shield assembly 1 i8 islowered. The arbors 40 and 42 may then be axially separated to allowremoval of the finished workpiece by manipulation of the togglemechanism.

Because of the force transmission path from the backup members 84 andthrough the fittings to the workpiece W, the arbors 40 and 42 andassociated mechanisms are freed from any substantial radial loads andthe workpiece runs in substantially exact coneentricity with its ownaxis. Further because of the location of the pilot surfaces 114 and 116of the fittings 44 and 46, respectively, immediately adjacent to theside faces of the workpiece, bending moments are reduced to a minimumand deflections in this system approach their minimum theoretical value.To impart further rigidity to the system and to reduce the number ofparts that must be manufactured to very close tolerances, the pairs ofbackup members 84 and 88 and 86 and 90 and their associated shafts 92and 94, respectively, may be formed integrally.

We claim:

1. Apparatus for roll forming a toothed workpiece comprising a toothedforming roll mounted for rotation about a predetermined axis, aworkpiece support assembly adapted to support a workpiece for rotationabout an axis essentially parallel to said predetermined axis and inrolling engagement with said forming roll, said support assemblycomprising a pair of support members, means for moving one of saidworkpiece support members to a predetermined locating position, means tomove the other member into clamping relation with said workpiece to holdsaid workpiece against said one support member at said locatingposition, thereby restraining said workpiece against movement along itsaxis, said support assembly having first and second cylindrical pilotsurfaces concentric with the rotational axis thereof, said first andsecond pilot surfaces being disposed, respectively, at opposite sides ofsaid workpiece, and means providing first and second pairs ofcylindrical backup surfaces, each pair being adapted to run in rollingcontact with one of said pilot surfaces.

2. The apparatus according to claim 1, wherein said workpiece iscentrally apertured and wherein one of said support members extendsthrough said central aperture and each of said support members has aradial surface adapted to engage the side radial surfaces of saidworkpiece.

3. The apparatus according to claim 1, wherein said backup surfaces aremounted for movement laterally of a plane con- 3 6 3 l 7 O4 5 6 tainingthe axis of said forming roll and the axis of said workpiece supportassembly between a rolling position and a loading position, the spacingbetween said forming roll and said backup surfaces being such as toprevent the movement of an oversized -workpiece to said rollingposition. 5

1. Apparatus for roll forming a toothed workpiece comprising a toothedforming roll mounted for rotation about a predetermined axis, aworkpiece support assembly adapted to support a workpiece for rotationabout an axis essentially parallel to said predetermined axis and inrolling engagement with said forming roll, said support assemblycomprising a pair of support members, means for moving one of saidworkpiece support members to a predetermined locating position, means tomove the other member into clamping relation with said workpiece to holdsaid workpiece against said one support member at said locatingposition, thereby restraining said workpiece against movement along itsaxis, said support assembly having first and second cylindrical pilotsurfaces concentric with the rotational axis thereof, said first andsecond pilot surfaces being disposed, respectively, at opposite sides ofsaid workpiece, and means providing first and second pairs ofcylindrical backup surfaces, each pair being adapted to run in rollingcontact with one of said pilot surfaces.
 2. The apparatus according toclaim 1, wherein said workpiece is centrally apertured and wherein oneof said support members extends through said central aperture and eachof said support members has a radial surface adapted to engage the sideradial surfaces of said workpiece.
 3. The apparatus according to claim1, wherein said backup surfaces are mounted for movement laterally of aplane containing the axis of said forming roll and the axis of saidworkpiece support assembly between a rolling position and a loadingposition, the spacing between said forming roll and said backup surfacesbeing such as to prevent the movement of an oversized workpiece to saidrolling position.